Re: [Xen-users] Live migration not moving the disk image. Is is supposed to?

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> > From: Stefan de Konink [mailto:skinkie@xxxxxxxxx]
> > Sent: Thursday, May 15, 2008 7:28 PM
> > To: Jamie J. Begin
> > Cc: xen-users@xxxxxxxxxxxxxxxxxxx
> > Subject: Re: [Xen-users] Live migration not moving the disk image. Is is
> > supposed to?
> >
> > On Thu, 15 May 2008, Jamie J. Begin wrote:
> > > >From my reading, it looks like performing "xm migrate -live domU
> > >
> > > target_server" ought to also copy the disk image.  Am I right?
> > >
> > > When I attempt this procedure, everything looks to work except for the
> >
> > image
> >
> > > file getting moved.  The command takes about 30 seconds to complete and
> >
> > then
> >
> > > "xm list" shows the domU to be gone from the old host and running on
> > > the
> >
> > new
> >
> > > host.  The SSH connection to the domU also continues to function
> > > without
> >
> > a
> >
> > > hiccup. However, the disk image isn't located anywhere on the new
> >
> > server.
> >
> > > Also, the xen log on the new server lists the following error:
> > >
> > > [2008-05-15 19:10:21 xend 3790] ERROR (XendCheckpoint:275) Device 51712
> > > (tap) could not be connected.
> > >
> > > /virt/myserver.img does not exist
> >
> > That sounds pretty much like expected behavior. This is why you require
> > something like NFS, DRBD, iSCSI to have the storage available over more
> > than one machine at a time.
> >
> >
> > Stefan
>
> Ok, thanks. I just wanted to make sure that this was expected behavior.
> Yeah, iSCSI is forthcoming for the production environment.  I'm just
> testing a few things here.

You do need to have the storage accessible from multiple machines in order to 
support live migration.  You can either do this by having dom0 access the 
storage (e.g. over SAN or network) and export it to the domU as a VBD (I 
recommend this, it's more transparent) or by setting up the domU to access 
its storage directly over the network (e.g. using iSCSI root or NFS root).

Xen includes some NBD-aware block scripts to make it easy to handle NBD-based 
block devices in an automated way.  Stefan has, I believe, published some 
iSCSI (and Netapp filer specific) block scripts on these mailing lists, which 
may also prove useful.

Cheers,
Mark

-- 
Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/)

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